What it does
BMW's E90 training lists the JBE's jobs: the gateway for the F-CAN, the wipe/wash system and heated washer jets, seat and mirror heating, the rear power windows and sun blind, the rear-window defogger, and the actual locking and unlocking of the whole car. It also reads the coolant-level, washer-fluid, fuel-level and handbrake inputs and passes them to the instrument cluster.
How it fails, and what gets replaced first by mistake
Because it carries so many unrelated jobs, a JBE fault produces a cluster of complaints that share nothing but this module — wipers, rear windows, locking, heated seats, and warnings from the sensors it reads for the cluster. Shops replace consumers one at a time while the common point is the fault.
Generations this applies to
From a documented source: BMW training ST502, E90 General Vehicle Electrical; BMW training, Power Management (E7x junction box).
Is this module acting up on your car?
I come to the car, read the modules and trace the fault to the actual wire, connector or module.
Run a repair or body shop? BMW programming support for shops